Muffled
Jesus in me
That Wikipedia page is pretty good at explaining why glossolalia is not considered a genuine human language. When I was an assistant professor of linguistics, we occasionally got calls from local groups about this. In one case, someone sent us a tape asking to identify the language being spoken. It was clearly not a real language, but a stream of nonsense syllables.
Every human language has a limited set of basic speech sounds called "phonemes". English has about 43 phonemes, but the inventory of sounds can vary. When you listen to English-based glossolalia, what you hear is a string of syllables comprised of two types of speech sounds--English phonemes and sounds that English speakers typically associate with a foreign accent (e.g. trilled "r"). What you almost never hear are some of the more exotic speech sounds that characterize real foreign languages--clicks, imploded stops, glottalized stops, pitch stress, tone differences, etc. In other words, the stream of syllables produced is exactly what you would expect if the speaker were making it all up and did not know much about what foreign languages are really like.
Now, Klingon--that is more authentic "speaking in tongues".
I once asked a linguist what the meaning of the Russian word aprunsenov meant. At least it sounded Russian to me. Later I realized that it was simply the acronymn that I used to remember the months with thirty days: April June September and November.